Answer: the correct option is D. (i) only.
Explanation: Monopoly is a market structure that is characterized by a single seller, selling a unique product in the market. Usually, in a monopoly market, the seller encounters little or no competition, and he/she is the sole seller of a particular product or service with no close substitute. He/she enjoys the power of setting the price for his goods.
In the scenario above, Amanda can only set the price of her service at whatever level she pleases. She can not force the customers to purchase her service, and neither can she achieve an unlimited level of profit, because the customers can choose not to purchase her service if the the price level is not favorable.